On structure and maturity changes of the Bohai Sea ecosystem during the 1980s-1990s

To quantify the historical ecosystem changes in the Bohai Sea, the Ecopath models (EWE 6.2) were developed in three time periods (1982-1983, 1992-1993 and 1998-1999), where measured data was available. The trends in the structure, maturity and keystone of the Bohai Sea ecosystem from 1982 to 1999 were assessed and planning and management measures were proposed. Numerical results indicated that (1) the ecosystem size of the Bohai Sea in terms of flow is becoming small; (2) the Bohai Sea has experienced a decline in maturity ascribed to the anthropogenic and natural factors; (3) the Bohai Sea ecosystem is in the developing state. In addition, organisms of the highest trophic level (trophic level >= 3.34), such as Squid, exert significant influences on the Bohai Sea ecosystem, but their biomass is declining. To alleviate and prevent further decline in the ecosystem size in terms of flow and maturity of the Bohai Sea, ecosystem-based management and abundance of organisms of the highest trophic level need to be considered in future conservation planning and management.